1. Field of the Invention
The invention relates to an electric power steering system that assists a vehicle steering operation.
2. Description of the Related Art
There is a known electric power steering system that assists a driver in performing a steering operation by applying assist torque generated by a motor to a steering mechanism of a vehicle. An electric power steering system of this type is described in Japanese Patent Application Publication No. 2006-151360 (JP 2006-151360 A).
The electric power steering system described in JP 2006-151360 A includes an input torque computing unit that computes an input torque on the basis of a steering torque and a steering angle, and a virtual steering model that sets a target steering angle (target steered angle) on the basis of the input torque computed by the input torque computing unit. The electric power steering system controls driving of a motor by executing feedback control for causing an actual steering angle (steered angle) to follow the target steering angle set by the virtual steering model.
With the electric power steering system described in JP 2006-151360 A, the actual steered angle of a vehicle follows the target steered angle irrespective of the operating state of the vehicle. Therefore, a driver may not be able to gain a steering feel corresponding to the operating state. This is one of the factors that it is difficult to gain a good steering feel.